A problem facing current medical development is the evolution of antibiotic resistant strains of a number of significant pathogenic microbes. An example of a pathogenic organism which has developed resistance to antibiotics is Staphylococcus aureus. S. aureus is a bacterium whose normal habitat is the epithelial lining of the nose in about 20-40% of normal healthy people and is also commonly found on people's skin usually without causing harm. However, in certain circumstances, particularly when skin is damaged, this germ can cause infection. This is a particular problem in hospitals where patients may have surgical procedures and/or be taking immunosuppressive drugs. These patients are much more vulnerable to infection with S. aureus because of the treatment they have received. Resistant strains of S. aureus have arisen in recent years. Methicillin resistant strains are prevalent and many of these resistant strains are also resistant to several other antibiotics. Currently there is no effective vaccination procedure for S. aureus. 
The present invention is concerned with the identification of potential vaccine components and therapies against which the problem of directly resistant pathogen strains is avoided or reduced.
Amongst the approximately 4100 genes in the soil gram-positive bacterium Bacillus subtilis chromosome, 271 are indispensable (“essential”) for growth and among them, 23 have undefined roles in the physiology of the organism (gcp, obg, ppaC-yybQ-, trmU, yacA, yacM, ydiB, ydiC, yjbN, ykqC, ylaN, yloQ, ylqF, ymdA, yneS, yphC, yqeH, yqeI, yqjK, yrvO, ysxC, ytaG, ywlC) (Kunst et al. 1997). Homologs of the proteins encoded by these genes can be found in the various strains sequenced thus far of another gram-positive bacterium, the human pathogen Staphylococcus aureus. Amongst them, the Gcp and YneS orthologs are predicted membrane proteins, while the rest are predicted cytoplasmic proteins (data not shown). Nonetheless, Obg has been shown to be partially bound to membranes in B. subtilis (Kobayashi et al. 2001).
The inventors have isolated certain polypeptides that are essential components for growth of the pathogens Bacillus subtilis and Staphylococcus aureus and have raised antisera against these polypeptides. Antisera raised against the Bacillus subtilis polypeptides was found to result in extremely potent killing of Staphylococcus aureus. This effect could not have been predicted.
The present findings facilitate the development of vaccines and antibody therapies that mitigate some of the problems of current therapies such as antibiotic resistance.